File not found error when using GridFSBucket openDownloadStream - node.js

Question

I am able to upload a file using openDownloadStream of GridFSBucket and see that the file is uploaded and visible under songs.files chunks. But for some reason, get the following error while trying to download it -
Caught exception: Error: FileNotFound: file def1.txt was not found
My code is -
var express = require('express');
var gridModule = express.Router();
var mongoose = require('mongoose');
var fs = require('fs');
gridModule.post('/', (req, res) => {
console.log("::::grid");
//const gridfs = new mongoose.mongo.GridFSBucket(mongoose.connection.db);
//const writeStream = gridfs.openUploadStream('test.dat');
var gridfs = new mongoose.mongo.GridFSBucket(mongoose.connection.db, {
chunkSizeBytes: 1024,
bucketName: 'songs'
});
fs.createReadStream('./def.txt').
pipe(gridfs.openUploadStream('def1.txt')).
on('error', function (error) {
assert.ifError(error);
}).
on('finish', function () {
console.log('done!');
process.exit(0);
});
});
gridModule.get('/', (req, res) => {
var gridfs = new mongoose.mongo.GridFSBucket(mongoose.connection.db, {
chunkSizeBytes: 1024,
bucketName: 'songs'
});
/* var bucket = new mongodb.GridFSBucket(db, {
chunkSizeBytes: 1024,
bucketName: 'songs'
}); */
gridfs.openDownloadStream('def1.txt').
pipe(fs.createWriteStream('./def1.txt')).
on('error', function(error) {
console.log(":::error");
assert.ifError(error);
}).
on('finish', function() {
console.log('done!');
process.exit(0);
});
});
module.exports = gridModule;
I tried using ObjectId id as well but same error. Anyone any guesses what I may be doing wrong here?
Note - Code may not seem optimized here like declaring bucket twice, kindly ignore it for now as I will correct it once it works.

Answer 1

According to the API doc here, in order to use filename as argument you should use
openDownloadStreamByName(filename, options)
not openDownloadStream. openDownloadStream takes id
of the file.

Answer 2

Another possible explanation for this, if you're already calling openDownloadStream and still experiencing the FileNotFound error, and you are 100% the id is correct, is that you didn't pass an ObjectId type.
In my case, I was passing an id string instead of an id as an ObjectId.
bucket.openDownloadStream(mongoose.Types.ObjectId(id));
vs
bucket.openDownloadStream(id);